Apparatus and method for cleaning of semiconductor process chamber surfaces

ABSTRACT

In accordance with the present invention, a temperature-controlled ceramic liner or barrier is used adjacent to process chamber surfaces during a plasma-comprising process, with the liner or barrier temperature being set to reduce the formation of deposits upon or to aid in the removal of deposits from the liner surface during the processing of a semiconductor substrate within the process chamber. In the alternative, cleaning of the process chamber surface is carried out after the semiconductor substrate is removed from the chamber, and the liner or barrier temperature is set to assist in the removal of deposits from the liner or barrier surface. Deposits accumulate on some process chamber surfaces faster than on others. Since the rate of deposit formation or removal is temperature dependent, the temperature-controlled ceramic liner may be constructed to enable independent temperature settings at different locations within the liner. When multiple temperature-controllable barriers are used, each barrier may be set at a different temperature in proportion to the deposit formation reduction or removal requirements in the area of the process chamber protected by the particular barrier. In a preferred embodiment of the invention, the plasma used either during the semiconductor substrate processing or during a cleaning process after removal of the substrate from the process chamber is generated externally from the process chamber and is fed into the process chamber through a conduit. The conduit or at least the interior surface of the conduit which contacts the plasma is comprised of a halogen-containing material. The halogen used in the conduit material may be selected in consideration of the active species which is to be fed through the interior of the conduit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to an apparatus and method for cleaningchemical vapor deposition (CVD), physical vapor deposition (PVD), andetch chamber surfaces. In particular, the apparatus provides for theapplication of heat to the surface which is to be cleaned. The heat maybe applied during the CVD, PVD, or etch processing of substrates, duringsubsequent cleaning operations (with the substrate removed), or both. Ina preferred embodiment of the invention, process chamber cleaningoperations are carried out after substrate removal, using an externallygenerated active species which is brought in contact with the surface tobe cleaned, with this surface raised to elevated temperatures inaccordance with the apparatus and method described herein.

2. Brief Description of the Background Art

Semiconductor processing involves a number of different chemical andphysical processes whereby minute integrated circuits are created on asubstrate. The integrated circuits are constructed using multilayers ofpatterns of various materials. Layers of material are created bycombinations of various processes, including chemical vapor deposition,physical vapor deposition, and epitaxial growth. Some of the layers arepatterned using photoresist masks and wet and dry etching techniques.Patterns are created within layers by the implanting of dopants atparticular locations. (The substrate upon which the integrated circuitis created may be silicon, gallium arsenide, glass, or any otherappropriate material). Many of the processes carried out withinsemiconductor processing reactors leave deposits on the walls of theprocess chamber which accumulate and become the source of harmfulparticulate matter which must be prevented from contaminating thesemiconductor devices as they are formed within the process chamber. Asthe dimension size of the semiconductor device has become ever smaller,the presence of particulate matter upon the surface of the semiconductorworkpiece has become ever more critical.

Deposits can be removed from the walls of processing chambers, gasdistribution plates and the like by dry cleaning using plasma-enhancedetching, or the processing chamber surfaces can be opened and wetcleaned manually. This latter procedure for removing contaminants fromthe processing chamber wall is very time consuming.

Descriptions of the interrelationship between plasma etching and plasmapolymerization, with emphasis on the plasma-surface interactions leadingto polymerization are presented in "Plasma Polymerization ofFluorocarbons in RF Capacitively Coupled Diode System" by E. Kay and A.Dilks, J. Vac. Sci. Technol. 18 (1) January, February 1981. Furtherdescription of the use of fluorine and chlorine containing gases inplasma etching is provided in "Today's Plasma Etch Chemistries", PeterH. Singer, Associate Editor, Semiconductor International, March 1988.These articles make it clear that the development of a successful etchchemistry requires a careful selection of input gas composition as wellas careful control of the process variables, including gas flow rate,chamber pressure and temperature, plasma energy, and systemconfiguration.

The deposits on plasma process chamber walls can be removed in a plasmaeither by ion bombardment or by chemical reaction. Chemical reaction ispreferred, since this method typically provides a more gentle means ofremoving deposits, avoiding the ion bombardment of process chambersurfaces. The most preferred way to remove deposits using a chemicalreaction is to convert the deposits to a volatile species which can bepumped from the process chamber. Thus, it is desired to provide a methodof chemical reaction which either prevents the formation of initialdeposits upon the process chamber surface or which converts the depositson process chamber surfaces to volatile species which can be easilyremoved from the process chamber.

In the alternative, the process chamber surfaces have been lined withremovable, disposable (or "out-of-chamber" cleanable) liners whichintercept depositing materials before they reach the process chambersurfaces. For example, U. S. Pat. No. 5,366,585 to Robertson et al.,issued Nov. 22, 1994, assigned to the assignee of the present invention,and hereby incorporated by reference, describes a method and apparatusfor protecting conductive, typically metallic walls of a plasma processchamber from the accumulation of contaminants thereon and from reactionwith a gas plasma. A ceramic barrier material, preferably of at least0.005 inches (127 mm) thickness, is used adjacent the conductiveportions of the reactor chamber and between the gas plasma and suchconductive portions to be protected. The ceramic barrier materialintercepts the deposit of contaminating compounds formed from the plasmawhich would otherwise deposit on the protected reactor chamber surfacesand thereby reduces a source of particulates. Further, the ceramicbarrier material, which reduces the amount of deposit formation, alsoenables cleaning of the reactor chamber using an etch plasma generatedfrom halogen-comprising gas without the etch plasma attacking protectedmetallic portions of the reactor or the electrostatic chuck used forholding an article (typically a semiconductor substrate) to be processedin a reaction chamber.

Preferably the ceramic barrier is in the form of a ceramic liner, wherethe liner comprises a material chosen from the group consisting of theoxides and fluorides of aluminum, magnesium, and tantalum. Mostpreferably, the liner is constructed from alumina.

U. S. Pat. No. 5,085,727 to R. J. Steger, issued Feb. 4, 1992, disclosesan improved plasma etching apparatus comprising an etch chamber havinginner metal surfaces coated with a conductive coating capable ofprotecting such inner metal surfaces from chemical attack by reactantgases such as halogen-containing gases used in the chamber during theplasma etching processes. In a preferred embodiment, a carbon coating atleast about 0.2 micrometers in thickness is formed on the inner metalsurfaces of the etch chamber by a plasma assisted CVD process using agaseous source of carbon and either hydrogen or nitrogen or both. Theconductive coating material is said to comprise a material selected fromthe group consisting of carbon, titanium nitride, indium stannate,silicon carbide, titanium carbide and tantalum carbide.

U. S. patent application, Ser. No. 08/278,605 of Law et al., filed Jul.21, 1994, assigned to the assignee of the present invention, and herebyincorporated by reference, describes a deposition chamber cleaningtechnique which uses a remote excitation source. The remote excitationsource is used outside of the process chamber to generate a reactivespecies which is then supplied to the process chamber to assist in drycleaning of the process chamber. A second, excitation source inside thechamber can be used to sustain the long lived species and/or to furtherbreak down the gas which serves as the source of the active species.Since the remote excitation source is relied upon to generate thereactive species, the local excitation source may be operated at muchlower power levels than are required in a conventional system.

The exterior excitation source described in the preferred embodiment isa microwave generator. However, any power source that is capable ofactivating the precursor gas can be used. For example, both the remoteand local plasmas can employ DC, radio frequency (RF) and microwave (MW)based discharge techniques. If an RF power source is used, it can beeither capacitively or inductively coupled to the inside of the processchamber. External activation of the reactive species can also beperformed by a thermally based, gas break-down technique, a highintensity light source, or an X-ray source, to name just a few.

PCT Patent Application Ser. No. PCT/US94/05619 of Bensen et al.,published on Dec. 22, 1994, discloses a microwave plasma reactorincluding a chamber for containing a gas to be energized into a plasmawith microwave energy, an electrode having two surfaces within thechamber. A first surface of the electrode radiates microwave energy toform the plasma proximate the radiating surface, and a second surface ofthe electrode receives microwave energy from a wave guide of coaxialconductor, which energy is transferred to the first, radiating surface.

European Patent Application No. 91308222.8 of Donald K. Smith, publishedApr. 15, 1992, describes a recirculating high velocity convective flowreactive system which is well suited to deposit large area diamondfilms. The system includes a reactor into which gas is introduced, a gasactivation region in the reactor, and a device for supplying energy tothe gas in the activation region. The system also includes an activatedgas surface interaction region in the reactor, spaced from theactivation region, for utilizing the activated gas, and a high velocitypump, for moving the activated gas from the activation region to theinteraction region by convection, while it remains active.

In general, the reactive species used for cleaning semiconductor processchambers are selected from a wide range of options, including thecommonly used halogens and halogen compounds. For example, the reactivegas may be chlorine, fluorine, or compounds thereof, e.g. F₂, CIF₃ NF₃,CF₄, SF₆, C₂ F₆, CCl₄, and C₂ Cl₆. Of course the particular gas that isused depends on the deposited material which is being removed. Forexample, in a tungsten deposition system, a fluorine compound gas istypically used to remove the deposited tungsten.

U. S. Pat. No. 4,960,488 to Law et al., issued Oct. 2, 1990, assigned tothe assignee of the present invention, and hereby incorporated byreference, describes a process for cleaning a reactor chamber. Theprocess is used to clean adjacent the RF electrodes and throughout thechamber and exhaust system.

The preferred embodiment describes the process parameters used in thedeposition of silicon dioxide upon a semiconductor wafer substrate. Inparticular, TEOS, oxygen and a carrier gas are inlet into the processchamber at a pressure of 0.5 to 200 Torr. The wafer substrate is heatedto about 375° C., the gas manifold plate is maintained at between about35° C. (to prevent condensation of TEOS thereon) and about 75° C. (abovewhich TEOS decomposes to a reactive species). The subsequent cleaningprocedure is designed to remove residual reactants and silicon dioxidefrom the process chamber.

The cleaning procedure is a two step continuous etch sequence. In thefirst step, relatively high pressure (2-15 Torr), close electrodespacing (160 mils, i.e. 4.06 mm), fluorocarbon gas chemistry (a mixtureof C₂ F₆ and O₂ at a C₂ F₆ :O₂ flow ratio of about 1:1 at about 100sccm) at an RF power of about 250-650 watts at 13.56 megahertz is usedfor etching the electrodes. In the second step, a lower pressure (500milliTorr-1 Torr) is used, in combination with a greater electrodespacing (400 mils, i.e. 10.16 mm), fluorocarbon gas chemistry (NF₃ at50-150 sccm), at an RF power of about 125-500 watts at 13.56 megahertz.No temperature ranges are provided for the cleaning procedure.

SUMMARY OF THE INVENTION

In accordance with the present invention, a temperature-controlledceramic liner or barrier is used adjacent to process chamber surfacesduring a plasma-comprising process, with the liner or barriertemperature being set to reduce the formation of deposits upon, or toaid in the removal of deposits from the liner surface during theprocessing of a semiconductor substrate within the process chamber. Inthe alternative, cleaning of the process chamber surface is carried outafter the semiconductor substrate is removed from the chamber, and theliner or barrier temperature is set to assist in the removal of depositsfrom the liner or barrier surface.

Deposits accumulate on some process chamber surfaces faster than onothers. Since the rate of deposit formation or removal is temperaturedependent, the temperature-controlled ceramic liner may be constructedto enable independent temperature settings at different locations withinthe liner. When multiple temperature-controllable barriers are used,each barrier may be set at a different temperature in proportion to thedeposit formation, reduction in formation, or removal requirements inthe area of the process chamber protected by the particular barrier.

In a preferred embodiment of the invention, the plasma used eitherduring the semiconductor substrate processing or during a cleaningprocess after removal of the substrate from the process chamber isgenerated externally from the process chamber and is fed into theprocess chamber through a conduit. When the plasma includes an activatedhalogen species, the conduit or at least the interior surface of theconduit which contacts the plasma is selected to comprise ahalogen-containing material. The halogen used in the conduit materialmay be selected so that it contains the same element as the activespecies which is to be fed through the interior of the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a semiconductor plasma processing chamber with atemperature-controlled ceramic liner in place within the chamber.

FIG. 2 shows a schematic of a the plasma processing chamber of FIG. 1with emphasis on the temperature-controlled ceramic liner and itsspacing from the temperature-conductive walls of the processing chamber.

FIG. 3 is a graph showing the relationship between temperature on thesurface of a temperature-controlled liner or barrier and the removalrate (cleaning rate) of a silica coating deposit from the surface of theliner or barrier.

FIG. 4 illustrates a general design for plasma distribution nozzles andthe conduit leading from the plasma source to the cleaning nozzles. Thecleaning nozzles make it possible to direct plasma active species towardthe surface which is to be cleaned. These nozzles and conduits leadingto these nozzles are preferably constructed from or lined with ahalogen-comprising material to avoid reduction in the active species ofa plasma passing through the conduits and the nozzles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention pertains to a temperature-controlled ceramic lineror barrier material which is used adjacent to process chamber surfacesduring a plasma-comprising process. The temperature of the ceramic lineror barrier is set to reduce the formation of deposits upon or to aid inthe removal of deposits from the liner surface during the processing ofa semiconductor substrate within the process chamber. In thealternative, the liner temperature is set to assist in the removal ofdeposits from the liner surface during a plasma cleaning processconducted after removal of the semiconductor substrate from the processchamber.

The temperature-controlled liner is comprised of ceramic, which offersthe particular advantage of being resistant to halocarbons attemperatures which may be as high as 900° C. In the majority ofapplications, the process temperature is less than about 400° C., andpreferably the process temperature is about 350° C. or less. With regardto the reduction in formation of residues on process chamber wallsduring production of a semiconductor device, the ceramic linertemperature setting depends on the process chemistry of the CVD, PVD oretch process which is being carried out. When the ceramic liner assistsin the cleaning of a reactor chamber after the semiconductor substratehas been removed, since the clean rate is typically exponential withtemperature, the ceramic liner temperature setting will be as high as ispractical, depending on the equipment involved. For example, thecleaning rate eventually becomes diffusion limited by the amount ofhalogen-containing plasma species which reaches the surface beingcleaned.

Metals, glass, resins, and ceramics are frequently used in the chemicalindustry as reactor materials. Reactor surfaces which come in contactwith halogens and halogen compounds must be designed forcorrosion-resistance. The plasma-generated active halogen species usedfor reactor cleaning in the semiconductor industry are particularlycorrosive. Although there are resins which will withstand these activehalogen species, such resins are typically have a short performance lifeat temperatures greater than about 100° C.

Although metallic materials such as stainless steels and high nickelalloy steels exhibit sufficient corrosion resistance, materialscontaining iron even in a small amount pose a problem because the ironmay cause surface defects on a silicon substrate in the presence ofhalogens, particularly fluorine. In general, we avoid the use of heavymetals for reactor surfaces when a sputtering process may be carried outwithin the reactor, since such heavy metals are readily transported tothe semiconductor substrate (wafer) during the sputtering process. Thefamiliar aluminum alloy reactor surfaces are not only attacked bycorrosive, halogen-containing plasmas, they further contain variousconstituents which form particulates upon exposure to halogen-containingplasmas.

Glass-comprising materials, such as borosilicate glass, are etchedrapidly in fluorine and are typically weak against heat shocks. Inaddition, many glasses are heavy in sodium, release of which endangersthe stability of the aluminum surface of the reactor as well as thesubstrate being processed in the reactor.

The preferred material of construction for the temperature-adjustableliner is a ceramic material which is substantially free (typically lessthan about 10 ppm) from transition metals and alkalis. Such ceramicmaterials have demonstrated excellent corrosion resistance in thepresence of halogen-containing plasmas.

The preferred ceramic material used to fabricate the liner isrepresented by the following formula:

    N.sub.a Y.sub.b

wherein N includes boron, aluminum, silicon, titanium, zirconium orchromium, Y includes oxygen, nitrogen or carbon. Typically, a is aninteger of 1-2 and b is an integer of 1-3. The ceramic material may alsobe a mixture of such materials.

Among the more preferred ceramic materials are oxides of alumina,silica, titania and zirconia, carbides such as silicon carbide, titaniumcarbide and zirconium carbide, and nitrides such as aluminum nitride,boron nitride, silicon nitride and titanium nitride. Of these materials,aluminum nitride has proved to be particularly compatible withsemiconductor processing.

The ceramic temperature-adjustable liner or barrier preferably utilizesa resistance heater as the embedded heating element which is used toadjust the temperature of the liner. The preferred heating element is aresistance heater, for example (and not by way of limitation) a flexibleetched foil heater or a wire-wound heating element. It is advantageousto select the material composition of the heating element so that thethermal expansion coefficient of the heating element matches to that ofthe liner or barrier ceramic. This increases the lifetime of thetemperature-controlled ceramic liner or barrier and prevents cracking ofthe liner or barrier which can reduce protection of the process chambersurface behind the liner or barrier.

Heat must be extracted from the liner in general, since the liner willabsorb heat during processing. Since it is desired to operate thevarious processes at temperatures greater than 100° C., water-containingcooling channels within the ceramic liner are not useful for extractingheat. Although there are some oils which can be used, this is not thepreferred manner of removing heat. Preferably a thermal drop (conductiveheat transfer means) which constantly draws heat out of the ceramicliner is used. The temperature of the liner is then controlled byoffsetting the thermal drop heat loss using the embedded heating elementand the plasma load. A thermocouple located upon or near the surface ofthe temperature-controlled ceramic liner or barrier detects the surfacetemperature and sends a signal to a controller, such as a commerciallyavailable SCR (silicon controlled rectifier) controller with aproportional integrating derivative (PID) loop which controls the powerto the embedded resistance heating element. In the present preferredembodiment, the nozzles and conduits used to feed activated plasmaspecies into the process chamber serve as thermal drops, as well astubes which provide access for the heater leads to the liner, and otherperipheral devices which lead from the process chamber to an exteriorlocation. One skilled in the art can envision any number of conductiveheat transfer devices. In some instances, an inert heat transfer gas maybe circulated between the aluminum alloy interior surface of the processchamber and the back side of the liner, with the inert heat transfer gasbeing constantly withdrawn from the process chamber to maintain thereduced pressure inside the process chamber.

In a preferred embodiment of the invention, the plasma used eitherduring the semiconductor substrate processing, or during a cleaningprocess after removal of the substrate from the process chamber, isgenerated externally from the process chamber and is fed into theprocess chamber through a conduit having at least its interior surfacecomprised of a halogen-containing material. In general, the conduit usedto transfer the active plasma from an externally-generated source isoperated at approximately room temperature. The halogen-containingmaterial which comprises the conduit material is preferably selected inconsideration of the active species which is to be fed through theinterior of the conduit. Examples of materials useful for at least theinterior surface of the conduit include materials which are generallysuitable for chlorine or fluorine service, such aspolytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE),perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP),ethylene-tetrafluoroethylene(ETFE),ethylene-chlorotrifluoroethylene(ECTFE), chlorinated polyvinylchloride(CPVC), polyvinylidine chloride (PVDC), polyvinylidine fluoride (PVDF)and the like.

The preferred embodiments described below are not intended to act as alimitation on the invention, but are used for illustrative purposes, asone skilled in the art can expand the concepts disclosed herein to thescope of the invention claimed herein.

EXAMPLES

It has been observed that the deposition rate for the silica coating ina SiH₄ -O₂ plasma is temperature dependent such that increasingtemperature (above that necessary to form the silicon dioxide) serves toreduce the deposition rate of the silica coating. Also, it has beenobserved that the rate of fluorine plasma cleaning of silica coatingsfrom chamber walls is increased with an increase in the temperature ofthe surface from which the silica coating is to be removed. Thus, bycontrolling the temperature of a surface, it is possible to reducedeposition or prevent deposition, or to increase the decomposition rateand removal of a deposit from a surface.

In the present instance, it is desired to produce a silica coating on asemiconductor substrate surface while avoiding deposition of a silicacoating on surrounding process chamber surfaces.

FIG. 1 shows a schematic of a lower section of a semiconductor processchamber 100 of the kind in which plasma-assisted chemical vapordeposition of coatings is carried out. The process chamber 100 includesan electrostatic chuck/susceptor 114 on which a semiconductor substrate(not shown) is held during processing. The process chamber walls 101 aresubject to the deposition of coatings generated by the chemical vapordeposition. In addition, since process chamber walls 101 are generallyconstructed from an aluminum alloy, the alloy may react with many of theactive species generated in plasma-assisted processing. To protect thealuminum alloy walls 101 of the process chamber from being coated bychemical vapor deposition materials, sputtered materials, etc., atemperature-controlled ceramic liner 102 is used. In the presentillustration, temperature-controlled ceramic liner 102 is made up of twosections, an upper section 104 and a lower section 106. Upper section104 contains an embedded resistance heater 110 and lower section 106contains an embedded resistance heater 108. Upper section 104 alsocontains a thermocouple 116 which enables detection of the temperatureof upper section 104, while lower section 106 contains a thermocouple118 which enables detection of the temperature of lower section 106.Each thermocouple, 116 and 118, is connected to a controller (not shown)such as a commercially available SCR (silicon controlled rectifier)controller with a proportional integrating derivative (PID) loop. Thecontroller for upper section 104 of ceramic liner 102 is used to controlthe temperature of that section, while the controller for the lowersection 106 of ceramic liner 102 is used to control the temperature ofthat section of the ceramic liner 102 independently. This makes itpossible to operate each section of ceramic liner 102 at the temperaturewhich provides the desired reduction in coating deposition duringchemical vapor deposition or sputter processing. Further, although thetemperature-controlled ceramic liner 102 does not completely isolate thealuminum alloy wall surfaces of the reactor from plasma-assistedprocesses, it reduces contact of the process chamber wall surfaces withthe corrosive plasmas, while acting as a partial barrier between asubstrate being processed interior to the liner and particulates whichare forming on process chamber wall surfaces. In addition, after removalof the substrate from the process chamber, the removal rate from a givensection of liner can be controlled during cleaning operations forremoval of coated or sputtered materials from the liner.

With regard to reducing or preventing the accumulation of silica andother deposits on process chamber surfaces during processing of asemiconductor substrate, the following example applies.

During plasma-assisted chemical vapor deposition of a silicon oxidecoating on the surface of a semiconductor substrate, when the depositrate of silica on the surface of lower section 106 oftemperature-controlled ceramic liner 102 is slower than the deposit rateon the surface of upper section 104, the temperature of lower section106 is set lower than the temperature of upper section 104.

For example, a typical silicon oxide coating was applied in a HDP CVDCentura® Reactor, available from Applied Materials, Inc. of Santa Clara,Calif. The process conditions for the plasma-assisted chemical vapordeposition included an RF generated plasma at 2.0 MHz and approximately2500 W, employing a pressure of about 0.01 to about 100 m Torr, and aself-bias voltage of about 0 to about 500 V. The gas flow rates wereapproximately 50 sccm SiH₄, 100 sccm of O₂, in combination with acarrier gas flow rate of about 100 sccm of Ar or Kr, with the surfacetemperature of the semiconductor substrate being at about 200° C. toabout 400° C.

The temperature of the lower section 106 of a temperature-controlledceramic liner 102 placed within process chamber 100, as shown in FIG. 1,was set at about 150° C., while the temperature of upper section 104 wasset at about 120° C. Without the presence of the temperature-controlledliner 102, the expected build up of silica on the lower aluminum surface103 of process chamber 100 typically ranged between about 4,000Angstroms and about 6,000 Angstroms per processing of 4×8,000 Angstrom 8in. diameter silicon wafers. With the temperature-controlled liner 102in place and with the sections of the liner set at the temperaturesspecified above, the expected build up of silica on the lower aluminumsurface 103, under the same deposition conditions, is typically lessthan about 3,000 Angstroms.

Upper section 104 of ceramic liner 102 may be cemented to or brazed to(not shown) lower section 106 of ceramic liner 102.

Depending on the temperature difference between thetemperature-controlled ceramic liner or barrier and the process chambersurface it protects, it may be advisable to leave a space between theliner or barrier and the process chamber surface. Typically,temperature-controlled ceramic liner 102 would be placed such that thespacing between the liner and face of the aluminum alloy process chamberwalls is about 0.5 mm. However, any spacing between the liner and theprocess chamber walls which avoids intimate contact is generallyadequate at the reduced pressures used for plasma processing and attemperatures below about 300° C. For example, with reference to FIG. 2,an insulating space 202 of about 0.5 mm (not to scale) between processchamber aluminum wall 101 surface 205 and the back surface 207 of theupper section 104 of temperature-controlled ceramic liner 102 isadequate. FIG. 2 also shows a space 206 between lower aluminum surface103 and the lower surface 209 of the lower section 106 oftemperature-controlled ceramic liner 102. Additional spacing such as 204between electrostatic chuck 114 and the lower section 106 of ceramicliner 102, and spacing 208 between nozzle 123 and the lower section 106of ceramic liner 102 helps prevent heat transfer between these elementswithin the process chamber.

There are some instances where the element to be cleaned can befabricated from a ceramic having an embedded heating element and thetemperature of the element itself can be adjusted during a cleaningprocess to assist in the removal of deposits from the surface of theelement. A good example of this is an electrostatic chuck fabricatedfrom aluminum nitride and containing an embedded heating element. Duringa plasma-assisted cleaning process, the temperature of the electrostaticchuck can be adjusted to that which provides the optimum reactivity ofthe deposit to be removed.

With regard to cleaning of the semiconductor process chamber 100 afterremoval of the semiconductor substrate from the chamber, the followingexample applies.

FIG. 3 shows a graph of the cleaning or removal rate for silicadepositions from a silica-coated test piece placed on a hot plate in aHDP CVD Centura® Reactor, for two different sets of process conditions.The data shows the temperature dependence relationship between thethickness of the deposit layer removed per minute and the temperature atwhich the cleaning process is carried out.

Under a first set of conditions, illustrated by line 302 on FIG. 3, theplasma-activated species was generated using an external 1400 Wmicrowave source, at a pressure of about 3.8 Torr, and with gas flowrates of approximately 1000 sccm of NF₃ and 100 sccm of Ar₂. Theexternally-generated, plasma-activated species produced were then passedthrough a tetrafluoroethylene conduit to the vacuum chamber of thereactor, entering through an entry port which was located top centerdirectly over a silica-coated (thermox-coated) silicon wafer chipapproximately 1 cm square which was attached (using a heat transfercompound) to the hot plate. The spacing between the plasma entry nozzlesurface and the test piece was approximately six inches (15.2 cm).

The equation representative of the removal rate (Clean Rate) "R",illustrated by line 302, for the silica coating from the test piecesurface using the externally-generated, microwave-activated speciesproduced from NF₃ is:

    R=166e.sup.-2109/T μ/min

where T is in °K

Thus, in terms of cleaning rate, at about 65° C., a deposit thickness ofabout 0.32μ was removed per minute; at about 150° C., 1.1 μ/min wasremoved; at about 200° C., about 1.9 μ/min was removed; and, at about250° C., about 2.9 μ/min was removed.

When the object is to remove all deposition materials from the surfaceof an aluminum alloy process chamber, production of a plasma-activatedspecies by localized ion bombardment of NF₃ typically drives fluorineinto the surface of the aluminum alloy as it becomes exposed. This leadsto the formation of AlF_(x). It is the AlF_(x) which forms a wispy filmthat peels off in time, forcing a wet clean down of process chamberwalls. The externally-generated, microwave-activated species producedfrom NF₃ enters the semiconductor processing chamber available to reactwith the surface of the deposits to be removed, without theabove-described harmful side effects.

Under a second set of conditions, illustrated by line 304 in FIG. 3, ahigh density plasma-activated species was generated within thesemiconductor processing chamber itself from a high density, inductivelycoupled plasma using RF at about 2 MHz and approximately 3500 W, at apressure of about 3.8 Torr, and with gas flow rates of approximately 200sccm of C₂ F₆ and 55 sccm Of O₂. The removal rate (Clean Rate) "R",illustrated by line 304, for the silica deposit was:

    R=16.1 e.sup.-2466/T μ/min

where T is in °K

Thus, in terms of cleaning rate, at about 250° C., a deposit thicknessof about 0.14μ was removed per minute; at about 300° C., 0.22 μ/min wasremoved; at about 350° C., about 0.32 μ/min was removed; and, at about400° C., about 0.429 μ/min was removed.

One skilled in the art can determine similar temperature relationshipsfor other plasma-activated species, and the relationship can be inputinto the temperature controller for the temperature-controlled ceramicliner section, to achieve the appropriate cleaning rate desired for agiven process chamber under the particular circumstances.

As described above, the plasma-activated species used to clean interiorsurfaces of semiconductor processing chambers can be generated withinthe chamber itself or can be externally generated. External generationnot only reduces the potential for damage to the reactor chamber wall,but also makes possible multiple point introduction of the plasma withinthe process chamber at various locations, so the plasma can be directedtoward particular process chamber surfaces which require specializedattention. Once inside the deposition chamber, the reactive species maybe further excited by a local activation source, if desired.

There are also process equipment handling advantages to aremotely-generated plasma, since it is not necessary to have a bulkyplasma-generation assembly attached to and disposed within the processchamber.

With regard to using multiple feed locations for the plasma-activatedspecies generated at a remote location, FIGS. I and 2 illustrate thenozzles 124 used to feed chemical vapor deposition materials intosemiconductor processing chamber 100 during the processing of asemiconductor substrate. Preferably nozzles 124 are extendable, toreduce the possibility of the build up of CVD materials on aluminum wall101 behind temperature-controlled ceramic liner 102. Extendable nozzles124 may also be used to feed plasma-activated cleaning species intoprocess chamber 100 during the cleaning of temperature-controlledceramic liner 102. Additional nozzles 123 are used to directionally feedplasma-activated cleaning species into the processing chamber 100.

Preferably, the additional nozzles 123 are extendable and rotatable toreach various heights and angles within process chamber 100, asillustrated in FIG. 1, where arrow 132 illustrates the extendibilityfeature and arrow 134 illustrates the rotatability feature. The means(not shown) for extending and rotating nozzles 123 is located beneaththe cleaning gas (plasma-activated cleaning species) conduits 121a and121b shown in FIG. 1. Conduits 121a and 121b each have an annular-shapedshoulder 126 disposed on their outer surface which comes to rest uponstop surface 128 when nozzle 123 is not extended. Stop surface 128resides within an annular-shaped well 127 within the lower aluminumsurface 103 of process chamber 100. An annular seal 130 between eachannular shoulder 126 and stop surface 128 helps maintain the pressuredifference between the deposition chamber reduced pressure and theambient pressure outside process chamber 100.

The means for extension and rotation of conduits 121a and 121b is notillustrated herein, but one skilled in the art can obtain commerciallyavailable motor driven mechanical devices to transfer the extension androtation motions to conduits 121a and 121b. The motor driven mechanicaldevices may be computer controlled, based on an algorithm which isrelated to the amount of deposit build up to be removed and its locationwithin the process chamber.

Preferably the flow rate of the plasma-activated species, thetemperature of the temperature-controlled ceramic liner or barrier, andthe extension and rotation of the nozzles from which theplasma-activated cleaning species flow are all coordinated and computercontrolled, to optimize deposit removal from the process chamber 100.

FIGS. 4a and 4b illustrate some possible nozzle designs which can beused in combination with conduits 120a and 120b which are used to feedexternally-generated, plasma-activated species into the semiconductorprocessing chamber 100. With reference to FIG. 4a, a cleaning gascontaining the active species is deflected upon deflection surface 406which is disposed at a 45° angle with respect to the axis 402 of 15 theconduit portion 404 of nozzle 400. The cleaning gas traveling throughconduit portion 404 of nozzle 400 are redirected to flow in anotherdirection 408 which is perpendicular to deflector axis 402, as indicatedby the flow arrows. In this manner, the active species can be appliedand focused on those areas within the semiconductor processing chamber100 which are normally difficult to reach. With reference to FIG. 4b,the cleaning gas traveling through conduit portion 424 of deflectornozzle 429 is redirected in two opposite directions, 426 and 428, bothof which are perpendicular to the deflector nozzle axis 422. In thismanner, additional areas can be simultaneously exposed to the cleaninggas and the active species contained therein.

Transportation of halogen-containing plasma-activated species throughvarious conduits from an external generation source to the semiconductorprocessing chamber offers the disadvantage of the potential fordeactivation of the activated species prior to their reaching thedesired area within the process chamber. For example, empiricalmeasurements have indicated that approximately 5 to 10% of the activityof externally generated, microwave-activated species produced from NF₃is lost per cm of linear travel through a stainless steel conduit(tubing) having an internal diameter of about 1.5 in. (3.8 cm), at aflow rate of 1,000 sccm, at a temperature of about 50° C., and at apressure of about 2 Torr. Similar measurements have indicated that, allelse held constant, approximately 0.13% of the activity is lost per cmof linear travel, when the activated species is passed through aluminumtubing. When tetrafluoroethylene (TFE) tubing is used, only about 0.04%of the activity is lost per cm of linear travel. Thus, it is importantto select the proper material for the internal surface of the conduitthrough which the active species travels to the semiconductor substrateprocessing chamber.

The above described preferred embodiments are not intended to limit thescope of the present invention, as one skilled in the art can, in viewof the present disclosure expand such embodiments to correspond with thesubject matter of the invention claimed below.

We claim:
 1. A temperature-controlled ceramic barrier which is usedadjacent to semiconductor process chamber surfaces during aplasma-comprising process, wherein said ceramic barrier temperature iscontrolled to reduce the formation of deposits upon, or to aid in theremoval of deposits from said ceramic barrier during the processing of asemiconductor substrate within said process chamber.
 2. Thetemperature-controlled ceramic barrier of claim 1, wherein the materialof construction of said ceramic barrier is selected from the grouprepresented by the following formula:

    N.sub.a Y.sub.b

wherein N includes boron, aluminum, silicon, titanium, zirconium, orchromium, and Y includes oxygen, nitrogen or carbon, and wherein a is aninteger of 1-2 and b is an integer of 1-3.
 3. The temperature controlledbarrier of claim 2, wherein said material of construction comprises amixture of materials, each of which is represented by the given formula.4. The temperature-controlled ceramic barrier of claim 1, wherein saidbarrier consists of multiple sections which have independentlycontrollable temperature settings.
 5. A temperature-controlled ceramicbarrier which is used adjacent to semiconductor process chamber surfacesduring the cleaning of said process chamber, subsequent to removal ofsemiconductor workpieces or substrates from said process chamber,wherein said ceramic barrier temperature is controlled to assist in theremoval of deposits from said barrier surface.
 6. Thetemperature-controlled ceramic barrier of claim 5, wherein the materialof construction of said ceramic barrier is selected from the grouprepresented by the following formula:

    N.sub.a Y.sub.b

wherein N includes boron, aluminum, silicon, titanium, zirconium, orchromium, and Y includes oxygen, nitrogen or carbon, and wherein a is aninteger of 1-2 and b is an integer of 1-3.
 7. The temperature-controlledceramic barrier of claim 6, wherein said material of constructioncomprises a mixture of materials, each of which is represented by thegiven formula.
 8. The temperature-controlled ceramic barrier of claim 5,wherein said barrier consists of multiple sections which haveindependently controllable temperature settings.
 9. A semiconductorprocessing device comprising a ceramic surface and having a means forcontrolling the temperature of said ceramic surface, wherein saidceramic surface temperature is controlled to reduce the formation ofdeposits upon, or to aid in the removal of deposits from said ceramicsurface during the processing of a semiconductor substrate.
 10. Thesemiconductor-processing device of claim 9 wherein the material ofconstruction of said temperature-controlled ceramic surface is selectedfrom the group represented by the following formula:

    N.sub.a Y.sub.b

wherein N includes boron, aluminum, silicon, titanium, zirconium, orchromium, and Y includes oxygen, nitrogen or carbon, and wherein a is aninteger of 1-2 and b is an integer of 1-3.
 11. Thetemperature-controlled semiconductor-processing device of claim 10,wherein said material of construction comprises mixture of materials,each of which is represented by the given formula.
 12. Thetemperature-controlled semiconductor-processing device of claim 9,wherein said temperature-controlled ceramic surface comprises multiplesections which have independently controllable temperature settings. 13.A semiconductor processing device comprising a ceramic surface andhaving a means for controlling the temperature of said ceramic surface,wherein said ceramic surface temperature is controlled during thecleaning of said semiconductor processing device to assist in theremoval of deposits from said ceramic surface.
 14. Thesemiconductor-processing device of claim 13, wherein the material ofconstruction of said temperature-controlled ceramic surface is selectedfrom the group represented by the following formula:

    N.sub.a Y.sub.b

wherein N includes boron, aluminum, silicon, titanium, zirconium, orchromium, and Y includes oxygen, nitrogen or carbon and wherein a is aninteger of 1-2 and b is an integer of 1-3.
 15. Thetemperature-controlled semiconductor-processing device of claim 14,wherein said material of construction comprises a mixture of materials,each of which is represented by the given formula.
 16. Thetemperature-controlled semiconductor-processing device of claim 13,wherein said temperature-controlled ceramic surface comprises multiplesections which have independently controllable temperature settings. 17.A method of reducing the formation of deposits upon, or aiding in theremoval of deposits from a temperature-controlled ceramic barrier in asemiconductor process chamber wherein said method comprises adjustingthe temperature of said temperature-controlled ceramic barrier during aplasma-assisted deposition process.
 18. The method of claim 17, whereinsaid plasma is generated at a location remote from said process chamber.19. A method of removing deposits from a ceramic barrier during acleaning process within a semiconductor process chamber, wherein saidmethod comprises adjusting the temperature of said barrier during aplasma-assisted cleaning process.
 20. The method of claim 19, whereinsaid plasma is generated at a location remote from said process chamber.21. A method for plasma-assisted cleaning of a semiconductor processingdevice comprising a ceramic surface, said method comprising:a) providinga means for controlling the temperature of said ceramic surface; and b)controlling the temperature of said ceramic surface to assist in theremoval of deposits from said ceramic surface.
 22. The method of claim21, wherein said temperature-controlled ceramic surface comprisesmultiple sections which are controlled to optimize contaminant removal.23. The method of claim 22, wherein the plasma used in saidplasma-assisted cleaning is generated at a location remote from saidcleaning process.
 24. A method for transporting a plasma-activatedspecies from a remote location to a plasma-assisted semiconductorprocessing chamber in a manner which reduces the inactivation of suchplasma-activated species during transport, said method comprising:passing said plasma-activated species through a conduit wherein at leastthe interior surface of said conduit, which contacts saidplasma-activated species, is comprised of a halogen-containing material.25. The method of claim 24, wherein a halogen present in said interiorsurface is selected based on compatibility with said plasma-activatedspecies which is to be fed through said interior of said conduit.
 26. Aconduit suitable for transporting a plasma-activated species from aremote plasma generation source to a plasma-assisted semiconductorprocessing chamber in a manner which reduces the inactivation of suchplasma-activated species during transport, at least an interior surfaceof said conduit being comprised of a halogen-containing materialselected based on compatibility with an active species which is to betransported through the interior of said conduit.
 27. The conduit ofclaim 26, wherein said plasma-activated species comprises fluorine andsaid conduit comprises tetrafluoroethylene.
 28. Thetemperature-controlled ceramic barrier of claim 1, wherein said barrieris in the form of a liner.
 29. The temperature-controlled ceramicbarrier of claim 2, wherein said barrier is in the form of a liner. 30.The temperature-controlled ceramic barrier of claim 3, wherein saidbarrier is in the form of a liner.
 31. The temperature-controlledceramic barrier of claim 4, wherein said barrier is in the form of aliner.
 32. The temperature-controlled ceramic barrier of claim 5,wherein said barrier is in the form of a liner.
 33. A semiconductorprocessing device comprising a temperature-controlled ceramic surface,wherein said ceramic surface temperature is controlled to reduce theformation of deposits upon or to aid in the removal of deposits fromsaid ceramic surface.
 34. A method of removing deposits from a ceramicbarrier during a cleaning process within a semiconductor processchamber, wherein said method comprises adjusting the temperature of saidbarrier.
 35. The method of claim 34, wherein said barrier is in the formof a process chamber liner.